The oracle's queen - Lynn Flewelling

Under the rule of a usurper king, the realm of Skala has suffered famine, plague,
and invasion.
But now the time for the rightful heir has come, a return to the tradition
of warrior queens.
And the Lightbearer's prophecy is to be upheld at last: so long
as a daughter of the royal line defends and rules, Skala will never be subjugated.

Now a mystical fire has burned away the male body known as Prince Tobin, revealing
Princess Tamr, a girl on the verge of womanhood-and a queen ready to claim her birthright
after a life in disguise under the protection of wizards and witches. But will her
people, her army-and the friends she was forced to deceive-accept her?
Worse, will
the crown's rival heir, friend to Tobin, turn foe to Tamr, igniting civil war in
a fierce battle for Skala?